Dense Cores Mapped in Ammonia: A Database

Abstract

We present a database of 264 cores mapped in the ( J , K ) = (1,1) and (2,2) lines of NH 3 . We list the core gas properties—peak positions, total ammonia column densities, intrinsic line widths, kinetic temperatures, volume densities, core sizes, aspect ratios, and velocity gradients, as well as the properties of associated young stellar objects (YSOs)—associated IRAS sources along with their luminosities and core-YSO distances, outflow velocities, and SIMBAD and cluster associations. We also present the results of our statistical analysis and enumerate important pairwise correlations among the various gas and YSO properties. The results indicate that the association of stellar clusters with star-forming cores has a greater impact on their properties than does the presence of associated YSOs within these cores, although the latter influence is also statistically significant. In other words, the difference in core properties (nonthermal line widths, kinetic temperatures, and core sizes) between cores with and without associated YSOs is less significant when compared with the difference in these properties between cores with and without cluster associations. Furthermore, core gas and YSO properties show a significant dependence on the star-forming region in which the core is located. For instance, cores in Orion have larger line widths, higher kinetic temperatures, and larger sizes compared with cores in Taurus. Similarly, YSOs in Orion are more luminous than those in Taurus. These cluster and regional dependencies seem important enough that they ought to be accounted for in any self-consistent theory of star formation. Finally, the ratio of starless to stellar cores is too small (8:12 in Taurus, 2:41 in Orion A) to be consistent with ambipolar diffusion timescales that predict ratios as high as 3-30. This result is true even for regions that are known to be well surveyed and not to suffer from significant sample biases.